Staphylococcus aureus is a gram positive bacterium and a common cause of nosocomial infections. Certain strains of Staphylococcus aureus are highly resistant to methicillin and related antibiotics due to the acquisition of the mecA gene, which encodes Penicillin Binding Protein 2a (PBP2a). These antibiotic resistant strains are known as Methicillin-Resistant Staphylococcus aureus, or MRSA, and their quick detection in samples is highly desirable for guiding effective patient therapy, and for preventing the spread of antibiotic resistant bacteria from infected patients or materials.
PBP2a prevents the binding of beta-lactam antibiotics, such as penicillins and cephalosporins, to mecA-encoding Staphylococcus, thereby conferring antibiotic resistance. Accurate and sensitive immunodetection of methicillin-resistant staphylococcus, including MRSA, via the presence of PBP2a, for example in a biosensor system, requires high-affinity and highly specific binding reagents. For example, Protein A, which is a protein produced by Staphylococcus aureus, and which is not associated with antibiotic resistance, has broad antibody- (e.g., IgG-) binding properties. In addition, for sensitive detection, PBP2a-binding agents are ideally directed against exposed regions or epitopes of PBP2a on intact or lysed cells, so as to allow sensitive detection of PBP2a.
Reagents, methods and systems for detecting antibiotic-resistant staphylococcus, including MRSA, in samples are needed, including high affinity and/or selective immunoreagents, as well as accurate and sensitive detection systems.